JP7155312B2 - Plating materials for electronic parts and electronic parts - Google Patents

Description

The present invention relates to plating materials and electronic parts.

Connectors, which are connecting parts for consumer and vehicle-mounted electronic devices, use materials obtained by plating the surface of brass or phosphor bronze with Ni or Cu underplating, and then further plating it with Sn or Sn alloy. . In recent years, Sn or Sn alloy plating is required to reduce the insertion force when fitting a male terminal and a female terminal formed by pressing a plated material.

In Patent Document 1, a substrate is plated as a base, then a first layer of Sn plating is applied, and further In plating having an average thickness of 1/2 or less of the first layer is applied thereon, followed by reflowing. It is described that a Sn—In alloy plating with a good appearance can be obtained by

Further, Patent Document 2 describes that a Sn plating layer is applied to the base material surface, Ag, Bi, Cu, In, and Zn plating is applied to the plating, and reflow treatment is performed.

Further, in Patent Document 3, a multilayer plating material having a first plating layer made of tin or a tin alloy on the outside of a conductive substrate and a second plating layer made of indium on the surface of the first plating layer is reflowed. described to be processed.

JP-A-11-279791 Japanese Patent Application Laid-Open No. 2002-317295 JP 2010-280955 A

However, with regard to the techniques described in Patent Documents 1 and 2, a method for reducing insertion force, which has been demanded in recent years, and a method for preventing characteristic deterioration in a high-humidity environment have not been clarified.

In addition, the technique described in Patent Document 3 is such that tin, tin-silver alloy, tin-bismuth alloy, tin-copper alloy, tin-silver-copper alloy, etc. are deposited on the surface of the conductive substrate under predetermined reflow conditions. Although the first plating layer and the second plating layer made of indium are formed on the surface of the first plating layer, there is room for further improvement in reflow conditions and plating configuration.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a plating material and an electronic component having a low insertion force (frictional force) and good high humidity durability.

As a result of intensive studies, the present inventors have found that the above problems can be solved by forming a base plating layer and a surface layer on a base material and forming each of these layers with a predetermined metal.

An embodiment of the present invention completed based on the above knowledge is specified as follows.
(1) a base plating layer made of Ni or a Ni alloy provided on the surface of the substrate;
A surface layer made of a Sn--In--Cu alloy provided on the base plating layer;
In the surface layer, a region with a higher Cu concentration than the surroundings observed by EPMA and a region with a lower Cu concentration than the surroundings are mixed . A plating material for electronic parts , having an area ratio of 50% or more .
(2 ) The plating material for electronic parts according to (1 ), wherein the surface layer has an area ratio of 30 atm % or more of In when observed by EPMA of 50% or more.
( 3 ) The plating material for electronic parts according to (1) or (2) , wherein the surface layer has an area ratio of 20 atm % or more of Cu when observed with EPMA of 90% or more.
( 4 ) An electronic component comprising the plating material for electronic components according to any one of (1) to ( 3 ).

According to the embodiments of the present invention, it is possible to provide a plating material and an electronic component having a low insertion force (frictional force) and excellent high humidity durability.

4 is a cross-sectional TEM image according to Example 1. FIG. 4 is a cross-sectional TEM image according to Example 2. FIG. 4 is a cross-sectional TEM image according to Example 3. FIG. 4 is a graph of each element concentration in the depth direction by line analysis according to Example 1. FIG. 10 is a graph of each element concentration in the depth direction by line analysis according to Example 2. FIG. 10 is a graph of each element concentration in the depth direction by line analysis according to Example 3. FIG. It is an EPMA observation photograph of a cross section of a surface layer in which a Cu-rich region and a Cu-poor region are mixed. 4 is an appearance observation photograph after a high-temperature and high-humidity test of a sample in which 40 pins functioning as male terminals are arranged in a row, according to Example 1. FIG. 4 is an appearance observation photograph before and after a high-temperature and high-humidity test according to Comparative Example 1. FIG.

Hereinafter, embodiments of the plating material and electronic component of the present invention will be described, but the present invention is not to be construed as being limited thereto, and as long as it does not depart from the scope of the present invention, based on the knowledge of those skilled in the art. Various alterations, modifications and improvements are possible.

<Configuration of plating material>
A plating material according to an embodiment of the present invention includes a base plated layer provided on a substrate, and a surface layer provided on the base plated layer.

(Base material)
The substrate is not particularly limited, but metal substrates such as copper and copper alloys, Fe-based materials, stainless steel, titanium and titanium alloys, aluminum and aluminum alloys can be used. Moreover, what combined the resin layer with the metal base material may be used. Examples of composites of metal substrates and resin layers include electrode portions on FPC or FFC substrates.

(underlying plating layer)
The base plating layer is provided on the substrate and is made of Ni or a Ni alloy. By forming the base plating layer with Ni or a Ni alloy, the hard base plating layer reduces the real contact area, makes it difficult to adhere, and reduces friction (insertion force). In addition, the underlying plating layer prevents the constituent metals of the substrate from diffusing to the surface layer, thereby improving heat resistance and solder wettability. The Ni alloy of the base plating layer can be composed of Ni and one or more selected from the compound group consisting of Cr, Mn, P, Fe and Co. When semi-bright Ni or bright Ni is used as the constituent metal of the underlying plating layer, an organic substance such as an additive such as S may be contained.

The Vickers hardness of the underlying plating layer is preferably about Hv 150-500. If the Vickers hardness of the underlying plating layer is less than Hv150, the influence on frictional force reduction is small, and if it exceeds Hv500, bending workability may deteriorate. More preferably, the Vickers hardness of the underlying plating layer is Hv 170-350.

(surface)
The surface layer is provided on the underlying plating layer and is made of a Sn--In--Cu alloy. According to such a configuration, since the surface layer contains Sn and In, the frictional force (insertion force) of the plated material is reduced. Moreover, since the surface layer contains Cu, the high-humidity durability of the plated material is improved.

The surface layer preferably has an area ratio of 5 atm % or more of Cu when observed by EPMA of 50% or more. According to such a structure, since the area ratio of Cu 5 atm % or more in the surface layer is 50% or more, the high humidity durability is further improved. From the viewpoint of further enhancing high-humidity durability, the area ratio of Cu 10 atm % or more in the surface layer is more preferably 50% or more, and even more preferably 60% or more.

The surface layer preferably has an area ratio of 30 atm % or more of In observed by EPMA of 50% or more. According to such a configuration, the area ratio of In 30 atm % or more when the surface layer is observed by EPMA is 50% or more, so the insertion force (frictional force) of the plated material is further reduced. From the viewpoint of further reducing the insertion force (frictional force), the area ratio of 30 atm% or more of In when the surface layer is observed with EPMA is more preferably 60% or more, and even more preferably 64% or more. .

The surface layer preferably has an area ratio of 20 atm % or more Cu of 90% or more when observed by EPMA. According to such a configuration, since the area ratio of 20 atm % or more of Cu is 90% or more when the surface layer is observed by EPMA, an increase in contact resistance after heating of the plated material is suppressed. From the viewpoint of further suppressing an increase in contact resistance after heating of the plated material, it is more preferable that the area ratio of Cu 20 atm % or more when the surface layer is observed by EPMA is 92% or more.

In the surface layer, a region having a higher Cu concentration than the surroundings and a region having a lower Cu concentration than the surroundings, observed by EPMA, may coexist. According to such a configuration, a Cu-rich region and a Cu-poor region coexist in the surface layer. Therefore, by adjusting the ratio of the Cu-rich region and the Cu-poor region, , the structure of the surface layer suitable for various characteristics. For example, by reducing the Cu-poor region, the contact resistance of the plated material can be kept low. FIG. 7 is an EPMA observation photograph of a cross section of a surface layer (Sn--In--Cu layer) showing a mixture of Cu-rich regions and Cu-poor regions. A thin region indicated by an arrow in FIG. 7 corresponds to a Cu-rich region, and a dense region indicated by an arrow in FIG. 7 corresponds to a Cu-poor region.

The Sn--In--Cu alloy forming the surface layer may contain (Cu ₇ In ₄ ) _x (Cu ₆ Sn ₅ ) _y in which a CuIn alloy and a CuSn alloy, called η phase, are mixed at an arbitrary ratio x:y, and τ2 It may also include Cu ₂ In ₃ Sn called phases, or Sn—In alloys. Also, the surface layer may contain Ni. In particular, the surface layer may contain Ni derived from the underlying plating layer.

<Manufacturing method of plating material>
As a method for producing a plating material according to an embodiment of the present invention, first, a Ni or Ni alloy layer is provided on a substrate, and Cu, In, and Sn are laminated in this order and plated. As the plating, wet (electrical, electroless) plating can be used. Alternatively, dry (sputtering, ion plating, etc.) plating or the like may be used. After plating, the plated material according to the embodiment of the present invention can be formed by performing reflow treatment (heat treatment).

The thickness and composition of the surface layer are determined by adjusting the reflow conditions, that is, the heating temperature and heating time. The reflow conditions are a maximum reaching point of 160 to 300° C., and a heating time of 8 to 20 seconds from room temperature to the reaching temperature.

(post-processing)
As described above, after the reflow treatment, the surface layer may be post-treated for the purpose of further reducing friction and improving whisker resistance and durability. Post-treatment improves lubricity and corrosion resistance, suppresses oxidation, and improves durability such as heat resistance and solder wettability. Specifically, contact oils and antioxidants for general electronic materials are applicable.

<Uses of plating materials>
Although the use of the plating material according to the embodiment of the present invention is not particularly limited, it can be used, for example, as a metal material for electronic parts. and FFC terminals or FPC terminals provided with a contact portion, and electronic parts provided with a metal material for electronic parts as an electrode for external connection. The terminal may be a crimp terminal, a soldered terminal, a press-fit terminal, or the like, regardless of the method of joining to the wiring side. External connection electrodes include connection parts with surface-treated tabs and surface-treated materials for semiconductor under bump metals.

Further, a connector may be manufactured using the connector terminals formed in this manner, and an FFC or FPC may be manufactured using the FFC terminals or the FPC terminals.

In addition, the plating material according to the embodiment of the present invention is provided with a female terminal connecting portion on one side and a board connecting portion on the other side of the mounting portion attached to the housing, and the board connecting portion is provided with a through-hole formed on the board. It may be used as a press-fit type terminal that is press-fitted into a hole and attached to the board.

Both the male terminal and the female terminal of the connector may be the plating material according to the embodiment of the present invention, or only one of the male terminal and the female terminal may be used. By using the plating material according to the embodiment of the present invention for both the male terminal and the female terminal, the adhesive friction force is further reduced and the insertion force is improved.

Examples of the present invention and comparative examples are given below, but they are provided for a better understanding of the present invention and are not intended to limit the present invention.

<Production of plating material>
As Examples 1 to 9 and Comparative Example 1, the following materials were subjected to electrolytic degreasing and pickling in this order. Next, under the conditions shown in Table 1, first plating, second plating, third plating, fourth plating, and reflow treatment were performed in this order to produce samples of the plating material. The thicknesses of the first to fourth platings can be appropriately determined according to the effect of reducing the insertion force and the reflow conditions.

(material)
(1) Plate material: thickness 0.20 mm, width 25 mm, component Cu-30Zn
(2) Male terminal: thickness 0.64 mm, width 0.64 mm, component Cu-30Zn

(First plating condition)
Matte Ni plating Plating method: Electroplating Plating solution: Ni sulfamate plating solution (JX Metal Trading Co., Ltd., Ni sulfamate plating solution 1014)
Plating temperature: 55°C
Current density: 0.5-10A/dm ²

(Second plating condition)
・Cu plating Plating method: Electroplating Plating solution: Cu sulfate plating solution (Cu concentration 60 g / L)
Plating temperature: 20-45°C
Current density: 1-10A/dm ²

(Third plating condition)
・ Sn plating Plating method: Electroplating Plating solution: Sn methanesulfonic acid plating solution (JX Metal Trading Co., Ltd., NSP-S200)
Plating temperature: 20-60°C
Current density: 0.5-10A/dm ²

(Fourth plating condition)
In plating Plating method: electroplating Plating solution: In plating solution (Japan Electroplating Engineers Co., Ltd., Microfab In4950)
Plating temperature: 30°C
Current density: 0.5-8 A/dm ²

(reflow treatment)
In the reflow treatment, the electric tubular furnace was set to 650 ° C., and it was confirmed with a thermocouple that the sample placed in the electric tubular furnace in the air atmosphere reached 160 ° C. to 300 ° C. The treatment time shown in Table 1 was and temperature.

<Evaluation>
Atomic Concentrations of Cu and In in Surface Layers The atomic concentrations of Cu and In in the surface layers of the samples according to Examples 1 to 9 and Comparative Example 1 were evaluated by the following evaluation methods.
First, using an EPMA: electron probe microanalyzer (JXA-8500F, manufactured by JEOL Ltd.), the surface of the sample was measured by area analysis under the conditions shown below.
Scanning: Stage scanning Applied current: 15.0 kv
Irradiation current: 2.5×10 ⁻⁸ A
Measurement magnification: 1000 times Time: 35 ms
Number of measurement points: 230 x 170
Measurement interval: (X axis, Y axis) = (0.50 μm, 0.50 μm)
Measurement area: (X axis, Y axis) = (115 μm, 85 μm)

Cross-sectional analysis Transmission electron microscope: Using a TEM (JEM-2100F manufactured by JEOL Ltd.), accelerating voltage: 200 kV, the results of cross-sectional analysis of the samples according to Examples 1, 2, and 3 are shown in FIGS. shown in

FIG. 1 shows a cross-sectional TEM image according to Example 1. As shown in FIG. FIG. 2 shows a cross-sectional TEM image according to Example 2. As shown in FIG. FIG. 3 shows a cross-sectional TEM image according to Example 3. As shown in FIG. The direction of line analysis is indicated by arrows in FIGS. In addition, as shown in FIG. 1, an alloy layer of the alloy of the surface layer and Ni may be generated at the boundary between the base plating layer and the surface layer.

4 (Example 1), FIG. 5 (Example 2), and FIG. 6 (Example 3) are graphs of each element concentration in the depth direction obtained by the line analysis. The analyzed elements are the composition of the surface layer and O and C. These elements are designated elements. Also, the concentration (at %) of each element was analyzed with the sum of the specified elements set to 100%. However, since C is an unavoidable impurity generated during cross-sectional processing (FIB processing) of the sample, only elements other than C are shown in FIGS. The structure of the surface layer of the sample was determined from the results of the elements other than C.

・Insertion force (initial insertion force)
The insertion force of the obtained sample was measured using a commercially available Sn reflow-plated female terminal (type 025 Sumitomo TS/Yazaki 090II series female terminal non-waterproof), and the males according to Examples 1 to 9 and Comparative Example 1 were plated. It was evaluated by performing an insertion/extraction test with the terminal.

The measuring device used for the test was 1311NR manufactured by Aikoh Engineering Co., Ltd., and the evaluation was performed with a sliding distance of the male pin of 3 mm. Five samples were used. As the insertion force, a value obtained by averaging the maximum values of each sample was adopted.

Contact resistance Contact resistance was measured by the four-terminal method using a CRS-G2050 type precision sliding tester manufactured by Yamazaki Seiki Laboratory Co., Ltd. with a contact load of 3N. In order to imitate a connector, a Sn-plated plate (Cu-30Zn plated with Sn to a thickness of 1 μm) was processed into a hemispherical shape of φ3 mm for the convex member of the contact portion. The contact resistance is shown in Table 2 as "initial contact resistance". In addition, the contact resistance of the sample after the atmospheric heating (180° C., 120 hours or more) test was measured and evaluated. The contact resistance is shown in Table 2 as "heat resistant contact resistance". Also, the resistance increase amount (R ₂ -R ₁ ) and the resistance increase rate ((R ₂ -R ₁ )/R ₁ ) x 100 [%] of the heat-resistant contact resistance (R ₂ ) with respect to the initial contact resistance (R ₁ ) asked.

- High Humidity Durability The high humidity durability was evaluated by the appearance of the sample after the high temperature and high humidity test. More specifically, for each of the conditions of Examples 1 to 9 and Comparative Example 1, a sample having 40 pins functioning as male terminals was prepared and left in an air atmosphere of 85° C. and 85 RT% for 240 hours. After that, the appearance of the center 20 pins excluding the 10 pins at both ends was visually evaluated. At this time, A was evaluated when no change (discoloration) was observed in appearance, and B was evaluated when a change was observed. FIG. 8 shows an appearance observation photograph after a high-temperature and high-humidity test of a sample in which 40 pins functioning as male terminals are arranged in a row in Example 1. As shown in FIG. FIG. 9 shows photographs of the external appearance of Comparative Example 1 before and after the high-temperature and high-humidity test. Referring to FIG. 9, it can be seen that the tab-side pin (the pin below the carrier in FIG. 9) has an increased white area after the high temperature and high humidity test, that is, a change in appearance occurs.

Also, the underlying plating layer is composed of matte Ni plating. In this case, the indentation hardness of the underlying plating layer is in the range of Hv 150-500.

Test conditions and evaluation results are shown in Tables 1 and 2.

(Evaluation results)
In each of Examples 1 to 9, a plated material having a low insertion force (frictional force) and good high-humidity durability was obtained. Also, the rate of increase in contact resistance was suppressed.

In Comparative Example 1, the main component of the surface layer is In plating and does not contain Sn, and if the mating member to be fitted is a Sn material, dissimilar metals will be joined and galvanic corrosion may occur. In addition, In is easily oxidized, and there arises a problem that it is difficult to use for connectors with low contact pressure. Moreover, the content of Cu was small, and the high humidity durability was poor.

Claims (4)

A base plating layer made of Ni or a Ni alloy provided on the surface of the base material;
A surface layer made of a Sn-In-Cu alloy provided on the base plating layer;
In the surface layer, a region with a higher Cu concentration than the surroundings and a region with a lower Cu concentration than the surroundings observed by EPMA are mixed ,
A plating material for electronic parts , wherein the area ratio of Cu 5 atm % or more when the surface layer is observed by EPMA is 50% or more . 2. The plating material for electronic parts according to claim 1 , wherein the surface layer has an area ratio of 30 atm % or more of In when observed by EPMA of 50% or more. 3. The plating material for electronic parts according to claim 1, wherein an area ratio of 20 atm % or more of Cu is 90% or more when the surface layer is observed by EPMA. An electronic component comprising the plating material for electronic components according to any one of claims 1 to 3 .

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